Train make-up and coupling operations typically involve high longitudinal force buff and draft impacts between the rail cars. End-of-Car cushioning devices are used to absorb these impacts, thus protecting the rail car and lading from damage. End-of-Car cushioning devices are connected to the coupling assembly of the rail car and generally configured to fit underneath the frame of the rail car, at both ends. In this configuration, the coupler of the rail car's coupling assembly is connected to the cushioning device. As such, forces exerted on the coupler are transmitted to the device. Normal in-train forces and impact forces are transmitted through the cushioning device. These devices generally use several gallons of hydraulic fluid to dissipate the several hundred thousand lbs-ft of kinetic energy, enabling the device to absorb impacts of 10 MPH or more, with an effective mass of one or two loaded rail cars.
Because most cushioning devices are configured to absorb high energy impacts instantly, one disadvantage of present devices are that they typically require orifice flow areas too large to appreciably resist the inertia of several rail cars. Especially if the rail cars are formed in a train together and have closing speeds of only one or two feet per second. In this situation, during compression and extension of the typical cushioning device, the device may only provide 10,000 to 20,000 lbs of hydraulic resistance, which is generally insufficient to cease movement of the rail car at such low speeds.
The combined effect of low hydraulic resistance between the cars at low speeds, in compression and extension, and low return spring forces can result in movement between the railcars generally referred to as free slack action. When a significant number of cars joined together in the train have end of car cushioning devices that allow free slack action to occur, resulting inter-car velocities between the rail cars can reach relatively high speeds. Such high inter-car velocities may result in detrimentally high forces between the trains. These undesirable high forces can lead to rail car damage, lading damage, coupler breakage, undesired brake emergencies, and possibly catastrophic rail car derailment.
Preloading is one method generally known to prevent slack action during train operation. Under preload conditions, a pressure relief flow control valve (or valves) is set, for example at the equivalent of 100,000 lbs-ft, and is added to the cushioning device to prevent the cushioning device from stroking until the force of impact between the rail cars exceed the preload force setting. In this arrangement, the cushioning device remains relatively rigid under most train handling conditions, but provides a cushioning effect during train make-up impact conditions. One disadvantage of preloading is that it is a relatively passive system. Additionally, if the preload force level is set for best train handling, it may be too high for protecting lading during impacts, especially with light railcars.
The ability to “lock out” the cushion device on command, preventing the cushioning device from stroking (i.e., extension and compression), can significantly reduce slack action and resulting inter-car velocities and forces. By locking out the cushioning device, thus preventing the device from stroking, a more rigid connection between the rail cars is created, enabling safer train operation, significantly improved ride-quality, and as a result, reduced lading damage. Furthermore, a rigid connection will enable the train to be operated at a high rate of speed.
Currently, the inventor is unaware of any cushioning device in operation that can be switched from cushion mode to locked mode. The AAR Mechanical Rules have provisions for blocking a cushion device from stroking by adding mechanical stops between the exterior moving sections. The purpose is to “lock out” a broken cushion device in order to transport the railcar to a repair facility.
Accordingly, it is desirable to provide a new cushioning device configured for on command locked out. It is desirable that such device: (1) provide impact protection between colliding rail cars during coupling operations; (2) enable on command lock out by positively controlling the stroke of the device via an electrically actuated fluid control shutoff valve; (3) fit existing rail car coupling systems and pocket configurations with little or no modification and; (4) operate using power and activation protocols compatible with existing braking systems.